Vista is actualy pretty good when gaming. DX 10 is faster even on DX 9 games so you get less hitching and more fps. You should look at 2 gig of ram upwards though. The only two problems I came across with vista is that it stores a lot of crap so you need a big hdd. Also, a good tip is to give the executable for the game, admin rights and run with compatability for xp sp2. This sorts out security issues.
The following is a list of games and emus I am running without problem.
Call of duty 1&2
F.E.A.R + F.E.A.R Extaction point
X2 the threat
Resident evil 4
Pro pinball ( big race, timeshock, fantastic journey )
Pure pinball 1 & 2
Splinter cell, pandora tomorow.
visual boy advance
BTW the codec’s that come with vista are crap. You’d want to put in a decent codec pack. I’m using klite and have updated macromedia flash for call of duty 2.
If you are a creative user then you will not normaly get eax, 3d sound etc unless you have an x-fi. For x-fi, you use a creative program called alchemy to get eax etc… back.